[Samsung Galaxy Nexus] waylo:
Sorry it took a while, here's some logcat.

First is just putting the phone over the back cover. I did not open your app:

01/15/2012 19:23:26 [WARNING] NFC-LLC(7950) bad LLC length byte 90

01/15/2012 19:23:26 [WARNING] NFC-LLC(7950) bad LLC length byte 33

01/15/2012 19:23:26 [WARNING] NFC-LLC(7950) bad LLC length byte 50

01/15/2012 19:23:26 [WARNING] NFC-LLC(7950) bad LLC length byte 0

01/15/2012 19:23:27 [WARNING] NFC_uart(7950) timeout!

01/15/2012 19:23:27 [WARNING] NFC-LLC(7950) LLC length mis-match

01/15/2012 19:23:27 [DEBUG] NfcService(7950) Tag detected, notifying applications

01/15/2012 19:23:27 [DEBUG] NativeNfcTag(7950) Check NDEF Failed - status = 255

01/15/2012 19:23:27 [DEBUG] NativeNfcTag(7950) Connect Failed - status = -1

This one I think I had your app open:

01/15/2012 19:23:34 [DEBUG] dalvikvm(29822) GC_CONCURRENT freed 499K, 5% free 14422K/15047K, paused 2ms+6ms

01/15/2012 19:23:37 [INFORMATION] System.out(459) UPDATECOUNTERS REQUEST: at.mroland.android.apps.nfctaginfo = 0

01/15/2012 19:23:37 [INFORMATION] System.out(459) UPDATINGCOUNTERS: at.mroland.android.apps.nfctaginfo = 0

01/15/2012 19:23:37 [DEBUG] dalvikvm(2847) GC_CONCURRENT freed 404K, 5% free 15376K/16071K, paused 5ms+8ms

01/15/2012 19:23:37 [INFORMATION] dalvikvm(2187) Turning on JNI app bug workarounds for target SDK version 10...

01/15/2012 19:23:37 [DEBUG] OpenGLRenderer(459) Flushing caches (mode 1)

01/15/2012 19:23:37 [VERBOSE] PhoneStatusBar(272) setLightsOn(true)

01/15/2012 19:23:37 [DEBUG] OpenGLRenderer(459) Flushing caches (mode 0)

01/15/2012 19:23:37 [DEBUG] dalvikvm(2187) GC_FOR_ALLOC freed 131K, 2% free 14291K/14535K, paused 14ms

01/15/2012 19:23:37 [INFORMATION] dalvikvm-heap(2187) Grow heap (frag case) to 14.750MB for 760016-byte allocation

01/15/2012 19:23:37 [DEBUG] dalvikvm(2187) GC_CONCURRENT freed 1K, 2% free 15032K/15303K, paused 1ms+2ms

01/15/2012 19:23:37 [DEBUG] NfcService(7950) Set Foreground Dispatch

01/15/2012 19:23:38 [VERBOSE] PhoneStatusBar(272) setLightsOn(true)

01/15/2012 19:23:38 [INFORMATION] ActivityManager(196) Displayed at.mroland.android.apps.nfctaginfo/.NFCTagInfo: +562ms

01/15/2012 19:23:39 [ERROR] Wifi_Multicast(29822) Error occurred while sending ping packet to ifb0.

java.net.SocketException: sendto failed: ENETUNREACH (Network is unreachable)

at libcore.io.IoBridge.maybeThrowAfterSendto(IoBridge.java:496)

at libcore.io.IoBridge.sendto(IoBridge.java:465)

at java.net.PlainDatagramSocketImpl.send(PlainDatagramSocketImpl.java:182)

at java.net.DatagramSocket.send(DatagramSocket.java:287)

at com.nullsoft.winamp.wifi.e.run(Unknown Source)

Caused by: libcore.io.ErrnoException: sendto failed: ENETUNREACH (Network is unreachable)

at libcore.io.Posix.sendtoBytes(Native Method)

at libcore.io.Posix.sendto(Posix.java:146)

at libcore.io.BlockGuardOs.sendto(BlockGuardOs.java:165)

at libcore.io.IoBridge.sendto(IoBridge.java:463)

... 3 more

01/15/2012 19:23:39 [DEBUG] dalvikvm(29822) GC_CONCURRENT freed 500K, 5% free 14422K/15047K, paused 4ms+3ms

01/15/2012 19:23:41 [DEBUG] NfcService(7950) Tag detected, notifying applications

01/15/2012 19:23:41 [DEBUG] NativeNfcTag(7950) Check NDEF Failed - status = 255

01/15/2012 19:23:41 [DEBUG] NativeNfcTag(7950) Connect Failed - status = -1

Also found this NFC related comment later:

01/15/2012 19:25:56 [DEBUG] NfcService(7950) Tag detected, notifying applications

01/15/2012 19:25:57 [DEBUG] NativeNfcTag(7950) Check NDEF Failed - status = 146

Hmm, looking back, I should be more dutiful in noting what I was doing when the errors were occurring! Sorry. Let me know if you need more.